What do holes and voids mean?

‘Voids’ can mean anything from cracks and crevices, up to the huge volume voids caused by a major tunnel collapse.

Holes and voids can be either concealed or open cavities that present naturally as a result of erosion and geological changes, or due to building, mining, and other commercial or industrial ground activity. Ranging from small to large, all holes and voids underneath structures will contain air, and possibly water, which can cause instability. Filling these spaces can prevent wider damage to the ground, on-ground structures, and the surrounding environment. Some holes and voids may need to be backfilled after operations cease, to prevent them becoming a hazard.

Large void in road being filled

Void in a commercial building being filled

What causes holes and voids?

Holes are often dug in mining, building, and infrastructure works, while voids may develop over time due to leaks and weather eroding sub-soils underneath a structure. Something as simple as a leaking pipe may wash away surrounding earth, creating voids (or an empty space) around the pipeline. Filling holes and voids ultimately aims to stabilise mines, tunnels, buildings, bridge approaches, bridge abutments, and other operating or decommissioned structures.

Likely causes:

Construction holes and excavation

Earthquake and seismic activity, often resulting in liquefaction



Joints in culverts

Land slippage

Leaking pipes washing away sub-soils

Abandoned tanks and pipelines

Mining and commercial operations

Poorly compacted fill

Water ingress

How to fix holes and voids

Mainmark has a number of solutions to address void-filling such as polyurethane grouting. We assess each situation to determine the best course of action and the best material to use. Smaller voids in underground rock strata are generally filled with a material like urea silicate or polyurethane resin that not only fills the void but also ‘glues’ the surrounding rock together. Urea silicate is the natural choice for coal mines due to its lower exothermic reaction temperature. Alternatively, when greater supportive strength is required large voids can be filled with urea silicate expanding resin.

Lightweight polymer modified cement is another option as the void fill material. Massive voids can be filled quickly and economically using a very low-density synthetic or cementitious-based fill material from our unique Terefil range. This solution can also be used across a variety of void-filling situations, including abandoned fuel tanks, pipelines, and manholes, voids behind seawalls, and quick-support, easy-flow backfill for service trenches.

Filling Holes and Voids under Infrastructure

Filling voids can re-support and prevent water ingress and erosion in critical infrastructure including rail, roads, highways, approach slabs, bridge approaches, bridge abutments, and airport runways. Mainmark offers a variety of means to fill underground voids to stabilise strata in tunnels and to strengthen the foundation ground under buildings and other on-ground structures.
We can also assist in decommissioning old infrastructure, including void filling of abandoned or redundant boreholes, culverts, tanks, manholes, pipes, and caverns. Voids around smaller pipelines are filled and leaks sealed from above using our Teretek engineered resin solution. If required, pipes can also be re-aligned and pavements re-supported.

In most cases, minimising downtime is the most important aspect. We concentrate on achieving the fastest response time possible, choosing applications and materials with the least impact and allowing the quickest recovery times for our clients.

Massive voids can be filled quickly and economically using a very low-density synthetic or cementitious material from our unique Terefil range. This engineered void fill solution can also be used across many situations, including decommissioning fuel tanks, pipelines and manholes, mass fill for sink holes, voids behind seawalls, and backfill for service trenches and manholes.

Benefits of Mainmark’s methods to fill holes and voids:

Quickly and safely decommissioning culverts, pipes and tunnels

Filling pipelines uphill or downhill without the filler spilling out

Stabilising bridge approaches and bridge abutments

Strengthening the foundation ground under buildings and other on-ground structures

Addressing land slippage around infrastructure

Retaining wall and wing wall backfill

Efficient and economical backfilling of services trenches and manholes

Mainmark hole and void filling methods used for Infrastructure: